Systems and methods for sensing intraocular pressure

ABSTRACT

Systems and methods of sensing intraocular pressure are described. An example miniaturized intraocular pressure (IOP) monitoring system is provided using a nanophotonics-based implantable IOP sensor with remote optical readout that can be adapted for both patient and research use. A handheld detector optically excites the pressure-sensitive nanophotonic structure of the IOP-sensing implant placed in the anterior chamber and detects the reflected light, whose optical signature changes as a function of IOP. Optical detection eliminates the need for large, complex LC structures and simplifies sensor design. The use of nanophotonic components improves the sensor&#39;s resolution and sensitivity, increases optical readout distance, and reduces its size by a factor of 10-30 over previous implants. Its small size and convenient optical readout allows frequent and accurate self-tracking of IOP by patients in home settings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/717,324, filed Dec. 17, 2012, which claims priority to U.S.Provisional Patent Application Ser. No. 61/576,493, filed Dec. 16, 2011,and U.S. Provisional Patent Application Ser. No. 61/601,464, filed Feb.21, 2012, all of which are incorporated by reference herein in theirentirety and for all purposes.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to optical sensors, and inparticular, to a system and method for sensing intraocular pressure.

Description of Related Art

Glaucoma is a leading cause of blindness, affecting an estimated fourmillion Americans and seventy million individuals globally. As glaucomatypically affects the elderly, the aging demographic trends indicatethat this disease will continue to be an ever-increasing socioeconomicburden to society. Elevated intraocular pressure (“IOP”) is a major riskfactor for glaucoma, and IOP monitoring is the single most importantclinical management tool.

Despite the pervasive use of IOP readings for disease monitoring and theclinically proven importance of the aggressive lowering of IOP, currentclinical management is primarily based on only periodic snapshots of IOPin the doctor's office obtained every few months. The inability ofpatients to easily monitor their own IOPs at different times of the dayor during various daily activities hinders the comprehensiveunderstanding of the IOP profile of individual patients and thepossibility of custom-tailored IOP control.

In addition to its use as a patient monitoring parameter, IOP is alsothe standard readout used in glaucoma research. However, achieving anacceptable level of accuracy and repeatability in animal IOPmeasurements requires anesthesia and extreme care. Conducting suchtime-consuming measurements in large populations of animals is a majorhurdle in glaucoma drug discovery.

The need for better IOP monitoring in clinical ophthalmology and indisease research has been widely appreciated. Existing measurementtechniques in clinical use measure IOP indirectly. Current IOPmeasurements involve a form of contact or noncontact applanationtonometry. However, both modalities have difficulties in providingreliable and repeatable readouts of actual IOP values inside the eye.All tonometers produce indirect IOP readings by deforming the ocularglobe and correlating this deformation to the pressure within the eye.Their readouts are heavily influenced by the corneal curvature andthickness, or corneal mechanical properties that vary due to co-existingocular pathologies. For example, patients who have received laserphotorefractive keratectomy have thinner corneas in the treated eyes andconsistently show lower IOP when measured using tonometry techniques.

Tonometry currently requires specialized equipment operated by anophthalmologist, optometrist, or skilled technician. Hence, IOPmeasurements are made typically in a doctor's office about two to fourtimes per year. Since studies show that IOP varies widely throughout theday, quarterly measurements are poor representations of a patient'sactual IOP profile.

A number of efforts have also been made to develop MEMS-basedimplantable IOP sensors with telemetric sensing. Unfortunately, theoperating principle of this device puts a limit on the miniaturizationof the sensor. Either the size of the sensor has to become large toachieve a longer transmission distance, or small devices lead toextremely short readout distances limit the practical use of the device.For example, to read IOP at a 2 centimeter distance, the IOP sensor hasto be at least around 3 millimeters in size, which is too large in termsof patient acceptance and interference with ocular function.

The identification of new therapeutic compounds for glaucoma treatmentutilizes IOP reduction in research animals as a screening parameter.Unfortunately, IOP measurements in animals using tonometry requireanesthesia and extreme care for repeatability. Previously developedMEMS-based sensors are too large for use in rodent models, which make upmore than 90% of the animal species used in glaucoma research. Forexample, these implants may range in size from 1-3 mm and are difficultto use in rodents that have corneal diameters of about 3.5 mm.

SUMMARY OF THE INVENTION

The above-described systems proposed a variety of techniques formeasuring and monitoring intraocular pressure (“IOP”). However, therestill exists a need for a highly miniaturized IOP monitoring system thatcan be adapted for both patient and research use. There also exists anunfulfilled need for a simple method to monitor IOP on a frequent basisat home, with easy, remote readout.

In view of the foregoing, one aspect of the present invention providesthe first engineered nanophotonics sensor for biological pressuresensing. Nanophotonic components reduce the size of the sensors, as wellas improve the sensitivity and strength of the readout signals.Embodiments of the invention provide a highly miniaturized IOPmonitoring system using a nanophotonics-based implantable IOP sensorwith remote optical readout that can be adapted for both patient andresearch use. A handheld detector optically excites thepressure-sensitive nanophotonic structure of the IOP-sensing implantplaced in the anterior chamber and detects the reflected light, whoseoptical signature changes as a function of IOP. Optical detectioneliminates the need for large, complexinductive-coupling/capacitive-sensing (LC) structures and simplifiessensor design. The use of precisely engineered nanophotonic componentsimproves the sensor's resolution and sensitivity, increases opticalreadout distance, and reduces its size by a factor of 10-30 overpreviously reported implants. Its small size and convenient opticalreadout allows more frequent and accurate self-tracking of IOP bypatients in home settings. In addition, this technology can be adaptedfor use in monitoring large cohorts of animals to support glaucomaresearch and drug discovery.

Thus, according to embodiments of the present invention, automated andsystematic monitoring of IOP profiles can be achieved. This leads tobetter definition of IOP fluctuations, that when combined withaggressive lowering of IOP, results in better clinical outcome. Itallows physicians to improve patients' adherence to medication anddetect suboptimal IOP control. It also provides more accurate IOPprofiles for individually tailored pressure-lowering treatment, andimproves understanding of the relationship between IOP and disease. Withadaptation, it also allows convenient IOP monitoring in large groups ofresearch animals to accelerated fundamental discovery and drugdevelopment.

In view of the foregoing, one aspect of the present invention provides amethod for sensing pressure, such as intraocular pressure. The methodcomprises establishing a gap between first and second membranes at afirst pressure, the first and second membranes comprising nanophotoniccomponents; transmitting a beam of light to the nanophotonic components;measuring a first reflectance of light off of the nanophotoniccomponents at the first pressure; changing the gap between first andsecond membranes in response to a second pressure; transmitting the beamof light to the nanophotonic components; measuring a second reflectanceof the light off of the nanophotonic components at the second pressure;and calculating the second pressure using the difference between thefirst reflectance of the light and the second reflectance of the light.

A device for sensing pressure, such as intraocular pressure, is alsoprovided according to an embodiment of the invention. The devicecomprises first and second membranes separated by a gap, the first andsecond membranes being configured to move with respect to each other inresponse to changes in pressure; and a plurality of nanophotoniccomponents embedded in the first and second membranes, the nanophotoniccomponents being configured to reflect light. A system for sensingpressure, such as intraocular pressure, is further provided according toan embodiment of the invention. The system comprises a device configuredto be implanted in an eye, the device comprising first and secondmembranes separated by a gap, the first and second membranes beingconfigured to move with respect to each other in response to changes inpressure, and a plurality of nanophotonic components embedded in thefirst and second membranes, the nanophotonic components being configuredto reflect light; and a reader configured to transmit light to thenanophotonic components and receive light reflected off of thenanophotonic components.

Still other aspects, features and advantages of the present inventionare readily apparent from the following detailed description, simply byillustrating a number of exemplary embodiments and implementations,including the best mode contemplated for carrying out the presentinvention. The present invention also is capable of other and differentembodiments, and its several details can be modified in variousrespects, all without departing from the spirit and scope of the presentinvention. Accordingly, the drawings and descriptions are to be regardedas illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given below and from the accompanying drawings of variousembodiments of the invention, which, however, should not be taken tolimit the invention to the specific embodiments, but are for explanationand understanding only.

FIG. 1A is a schematic diagram of a system for sensing intraocularpressure in accordance with an embodiment of the invention.

FIG. 1B is a close-up schematic diagram of the system for sensingintraocular pressure shown in FIG. 1A.

FIG. 2A is a front view of a system for sensing intraocular pressure inaccordance with an embodiment of the invention.

FIG. 2B is a perspective view of the system for sensing intraocularpressure shown in FIG. 2A.

FIG. 2C is another perspective view of the system for sensingintraocular pressure shown in FIG. 2A.

FIG. 2D is a close-up perspective view of the system for sensingintraocular pressure shown in FIG. 2A.

FIG. 2E is a close-up perspective cutaway view of the system for sensingintraocular pressure shown in FIG. 2A.

FIGS. 3A-3E are schematic diagrams of systems for sensing intraocularpressure in accordance with embodiments of the invention.

FIG. 4A illustrates pressure-sensitive bilayer-membrane disks at a firstpressure according to an embodiment of the invention.

FIG. 4B illustrates pressure-sensitive bilayer-membrane disks at asecond pressure according to an embodiment of the invention.

FIG. 4C is a graph illustrating the relationship between IOP and the gapbetween the pressure-sensitive bilayer-membrane disks illustrated inFIGS. 4A and 4B.

FIG. 4D is a graph illustrating the relationship between resonancewavelength and reflectance of the nanoparticles of thepressure-sensitive bilayer-membrane disks illustrated in FIGS. 4A and4B.

FIG. 4E is a graph illustrating the relationship between IOP and theshift in reflectance of the nanoparticles of the pressure-sensitivebilayer-membrane disks illustrated in FIGS. 4A and 4B.

FIG. 5A illustrates COMSOL simulation results of a sealed Parylene-Cbilayer-membrane disk according to an embodiment of the invention.

FIG. 5B illustrates COMSOL simulation results of a sealedbilayer-membrane disk at maximum deformation of the membranes accordingto an embodiment of the invention.

FIG. 5C is a graph illustrating the relationship between IOP and theintermembrane gap according to an embodiment of the invention.

FIG. 6A is a schematic diagram illustrating a Parylene-Cbilayer-membrane disk embedded with gold nanospot arrays according to anembodiment of the invention.

FIG. 6B is a graph illustrating the reflectance spectra of theParylene-C bilayer-membrane disk illustrated in FIG. 6A as a function ofthe intermembrane gaps.

FIG. 6C is a graph illustrating the shift in resonance of the Parylene-Cbilayer-membrane disk illustrated in FIG. 6A as a function of theintermembrane gaps.

FIG. 6D is a graph illustrating the shift in resonance of the Parylene-Cbilayer-membrane disk illustrated in FIG. 6A as a function of IOP.

FIG. 7 is a schematic diagram of an on-bench characterization chamberfor characterizing a system for sensing intraocular pressure accordingto an embodiment of the invention.

DETAILED DESCRIPTION

Systems and methods for sensing intraocular pressure (“IOP”) aredescribed. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the exemplary embodiments. It is apparent to oneskilled in the art, however, that the present invention can be practicedwithout these specific details or with an equivalent arrangement.

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, FIGS. 1Aand 1B are schematic diagrams of a system for sensing intraocularpressure in accordance with an embodiment of the invention. Abattery-free IOP-sensing implant 130 with remote optical readout isinserted into the ocular anterior chamber of an eye 120, between thecornea and the iris. The sensor implant 130 is excited by an excitationbeam 140 from an external light source built into a portable, handheldreader unit 110. The reader unit 110 scans the implant 130 over a rangeof wavelengths (e.g., from 750 nm to 1300 nm). The reflected light 150from the implant 130 over the range of wavelengths is used to locate adip in reflectance (i.e., a sudden decrease in reflectance). This dip inreflectance is then used to determine the current intraocular pressure(“IOP”) inside the eye 120, as described further herein.

FIGS. 2A-C are front and perspective views of a system for sensingintraocular pressure in accordance with an embodiment of the invention.In this embodiment, a plurality of battery-free IOP sensing implants 230with remote optical readout are inserted into the ocular anteriorchamber of an eye 220, between the cornea and the iris. The sensorimplants 230 are excited by an excitation beam 240 from an externallight source built into a portable, handheld reader unit 210. Thereflected light 250 from the implants 230 contain information on thecurrent IOP inside the eye 220.

FIG. 2D is a close-up perspective view of an implant 230. FIG. 2E is aclose-up perspective cutaway view of the implant 230 embedded with aplurality of nanophotonic components 237, described in further detailherein. Nanophotonic components 237 may comprise gold in one embodiment,such that nanophotonic components 237 are gold nanospots. Although shownand described as having a circular or cylindrical shape, it iscontemplated that nanophotonic components 237 may take on any shape,such as triangles or squares. Further, although illustrated as opaque inFIGS. 2A-E, it is contemplated that implants 230 are opticallytransparent in the range of sensing wavelengths.

FIGS. 3A-E are schematic diagrams illustrating various IOP-sensingconfigurations that can be established using IOP sensing implants andreaders 310 at home, hospitals, research labs and animal facilities witheasy optical readout according to embodiments of the invention. FIG. 3Ashows a user 360 using a reader unit 210 in handheld mode. FIG. 3B showsthe reader unit 310 scanning an implant while the user 360 uses computer370. FIG. 3C shows the reader unit 310 scanning an implant while theuser 360 is in the bathroom near mirror 380. FIG. 3D shows the readerunit 310 scanning an implant while the user 360 is watching television390.

FIG. 3E shows the systematic tracking of the IOP of a research mouse 365by a plurality of reader units 310 a and 310 b. The position andorientation of the head of mice are very predictable, and thus suitablefor IOP sensing by reader units 310 a and 310 b when consuming water orfood. In one embodiment, the collected IOP data is matched with thespecific animal sensed (in this case, mouse 365) through the use ofimplanted electronic ID tags. Thus, a single IOP detection device (suchas reader unit 310 b) can be used to monitor a whole group of animals.

FIGS. 4A-B illustrate a small-scale, implantable pressure sensor 400according to an embodiment of the invention. The sensor 400 comprisestwo pressure-responding flexible mechanical structures, in this casepressure-sensitive bilayer membrane disks 439 a, 439 b, embedded with aplurality of nanophotonic components 437 whose reflection spectrumvaries as the geometry of the hosting structure changes in a predictableway as a function of IOP. Nanophotonic components 437 may benanoparticles and/or nano-patterns having a pitch p and diameter d.

In this embodiment, force-resisting mechanical flexures 435 a and 435 b(e.g., springs) are used simply to represent the spring constant k_(y)of membrane disks 439 a, 439 b, and no flexures 435 a and 435 b areactually physically present. Because membrane disks 439 a, 439 bcomprise flexible and/or deformable materials, actual, physical flexures435 a and 435 b are not necessary to realize a spring constant k_(y).However, in other embodiments, it is contemplated that rigid membranesmay be implemented as membrane disks 439 a, 439 b, and thatforce-resisting mechanical flexures 435 a, 435 b (of any material havinga spring constant k_(y)) can be physically present in order to separatethe membranes and provide the appropriate change in gap, and describedfurther herein.

The initial intermembrane gap g_(o) narrows to a second intermembranegap g₁ as the ambient pressure P increases. Reference numeral 440represents the light incident on the surface of membrane 439 a. As thegap g becomes smaller, the resonance of the nanophotonic structures onthe membrane shifts (i.e., a reflectance dip), changing the opticalspectrum of the beam 450 that reflects off its surface. In other words,a change in intraocular pressure leads to a change in membranedeformation, causing a change in the gap size. The change in gap size,in turn, causes a shift in resonance (i.e., reflectance dip). By using apreviously obtained relationship between intraocular pressure andresonance shift, an accurate IOP reading can be made with the shift inresonance dip.

FIG. 4C is a graph illustrating the relationship between IOP and the gapbetween the pressure-sensitive bilayer-membrane disks 439 a, 439 billustrated in FIGS. 4A and 4B. FIG. 4D is a graph illustrating therelationship between wavelength of incidental light and reflectance ofthe nanophotonic components 437 of the pressure-sensitivebilayer-membrane disks 439 a, 439 b illustrated in FIGS. 4A and 4B. Δsrepresents the shift of the resonance (i.e., the sudden decrease or dipin the reflectivity) caused by the change in gap from g_(o) to g₁. FIG.4E illustrates the shift of resonance, Δs, as a function of IOP. In thepseudo-linear region, an IOP reading can be easily and reliablyobtained.

In one embodiment, simple, reliable mechanical designs and biocompatiblematerials are used in the disclosed systems for sensing IOP. Forexample, a Parylene-C bilayer membrane disk 500 can be used, as shown inFIG. 5A. Although shown and described with respect to a Parylene-Cbilayer membrane disk, however, it is contemplated that several othermaterials and techniques may be used to transform the IOP change intopredictable mechanical deformation. FIG. 5A illustrates exemplarydimensions of a Parylene-C bilayer membrane disk 500 (diameter=100 μm;thickness=2.1 μm; initial gap=1.525 μm). However, it is contemplatedthat other dimensions may be used to achieve similar results.

Finite element method (FEM) simulation results are shown in FIGS. 5B and5C showing the deformation properties of the Parylene-C bilayer membranedisk 500. FIG. 5B illustrates the maximum intended deformation of themembranes of the Parylene-C bilayer membrane disk 500. As shown in FIG.5C, the gap between the membranes varies linearly as a function of IOPbetween 1525 nm (at 0 mmHg) and 1150 nm (at 50 mmHg), at a rate of −7.5nm/mmHg. As understood by one skilled in the art, the design parametersof the Parylene-C bilayer membrane disk 500 can be modified to make themembrane disk 500 more or less sensitive (e.g., 50 nm/mmHg or 1 nm/mmHg)to environmental pressure changes.

Any nanophotonic structures may be implanted into the Parylene-C bilayermembrane disk 500 (or other suitable bilayer membrane disk). Forexample, as shown in FIG. 6A, high-Q nanospot arrays 602 may be embeddedinto a Parylene-C bilayer membrane disk 600. In this example, nanospotarrays 602 comprise gold. It is contemplated, however, that nanospotarrays 602 may alternatively or additionally comprise any number ofother suitable materials, such as silver, or other bio-compatible metalsor dielectric materials with proper optical properties, i.e., refractiveindex; transmission, reflection, and/or absorption rates in thewavelength range of interest (750 nm to 1300 nm).

The diameter of the nanospots, the pitch of the array, the refractiveindices of the membrane material and surrounding medium, and the gapbetween the membranes determine the resonance wavelength, resonancequality factor, free spectral range (FSR), and number of modes insidethe FSR. As shown in FIG. 6B, as the gap decreases, the dip in thereflectance, which is caused by the resonance of the bilayer membranesembedded with the nanophotonic structures, shifts to lower wavelengths.Because the light absorption in the cornea and in aqueous humor startsto increase rapidly for light above 1300 nm, the most useful opticalwindow according to embodiments of the invention exists between 750 nmand 1300 nm.

Turning back to FIG. 6A, the spot diameter, array pitch, andintermembrane gap are 240 nm, 400 nm, and 1.525 μm, respectively. Withthese design parameters, when the gap decreases from 1450 nm to 1150 nmdue to increasing IOP, the resonance (i.e., the dip in the reflectance)shifts from about 1300 nm to above 1060 nm, as shown in FIGS. 6B and 6C.This is equivalent to about a 240 nm shift over a 40-mmHg change (i.e.,from 10 mmHg to 50 mmHg), or a rate of 6 nm/mmHg, as shown in FIG. 6D. A6-nm shift of a sharp, high-Q resonance dip can be resolved usingcommercial miniature spectrometers or detected by using a photodiodeafter converting the wavelength shift to the intensity change based oninterferometric techniques. The final mapping between resonance shiftand IOP as shown in FIG. 6D is linear.

A number of advantages can be realized by using the disclosednanophotonic approach. For example, the disclosed implant has a simple,small structure that can be easily fabricated. Compared to an opticaltechnique that relies purely on the interference between the twodielectric surfaces, the addition of nanophotonic components doubles thequality factor of the resonance dip in the reflectance spectrum andachieves larger than 90% swings in reflectivity at resonance. Inaddition, within a circular area with a diameter of 100 μm on themembrane, an array of approximately 8,000 nanophotonic components can befit due to their extremely small, nanoscale dimensions. This highpacking density enables the 100 μm diameter implant to generate strongreflective optical signals that can be detected from a remote distanceover 20 cm.

FIG. 7 is a schematic diagram of an on-bench characterization chamber700 for characterizing a system for sensing intraocular pressureaccording to an embodiment of the invention. The chamber 700 simulatesan ocular environment in which the disclosed IOP sensors may be used andtested to optimize performance. The chamber 700 includes saline solution711; flow regulator 713 for regulating the flow of saline solution 711;valve 714 for controlling the access of saline solution 711 to pressurechamber 716; gas 723; pressure regulator 721 for regulating the pressureof gas 723; and valve 718 for controlling access of gas 723 to pressurechamber 716.

The chamber 700 simulates the environment of the anterior chambers ofhuman/rodent eyes, allowing the testing of the sensors in air as well assaline solution. The following tests and observations can be performedor made using the chamber 700: optical resonant frequency and quality(Q) factor of the nanophotonic array; vertical mechanical resonantfrequency and Q factor of the bilayer-membrane disk; the membrane'smechanical responsivity at heartbeat frequencies; pressure sensitivity,responsivity, and drift; temperature influence; dependence of remotereadout distance on sensor size and distance; and observation onbiological medium (viscosity) effect. These outcomes and findings can beused to optimize performance of the disclosed IOP sensors in oneembodiment.

In the past decade, large NIH-sponsored clinical trials have establishedthat tight IOP control leads to better clinical outcome. In addition, ithas been proposed that diurnal variations in IOP are important for theoptimal management of disease. Because IOP can be monitored frequentlyduring the course of a day according to embodiments of the invention,the readings can be stored for analysis and used to prompt patients toadhere to medications and to notify the physician about suboptimal IOPcontrol. The disclosed sensors can also serve as a sensing arm for drugdosing, much like the use of glucose sensors to inform diabetic patientsof the needed medication. As non-compliance to medication is known to bea major factor in treatment failure, convenient home monitoring of IOPwill improve patient compliance with medication and treatment outcomes.More accurate IOP profiles from individual patients also allow for thedevelopment of tailored medication protocols for individual patients toincrease clinical efficacy. In addition, the disclosed embodiments willprovide doctors with more detailed IOP tracking to understand therelationship of IOP to disease in a given patient, and to use thisinformation for improved clinical management. Given its highlyminiaturized form, IOP sensors according to embodiments of the inventioncan be used not only in humans, but also to record IOPs automaticallyfrom research animal colonies, thus assisting in the development of newdrugs for glaucoma therapy.

The present invention has been described in relation to particularexamples, which are intended in all respects to be illustrative ratherthan restrictive. Those skilled in the art will appreciate that manydifferent combinations of materials and components will be suitable forpracticing the present invention. For example, although shown anddescribed with respect to sensing intraocular pressure, it iscontemplated that the present invention can be modified to sensepressure at any location within or outside of the body.

Other implementations of the invention will be apparent to those skilledin the art from consideration of the specification and practice of theinvention disclosed herein. Various aspects and/or components of thedescribed embodiments may be used singly or in any combination. It isintended that the specification and examples be considered as exemplaryonly, with a true scope and spirit of the invention being indicated bythe following claims.

What is claimed is:
 1. A system for sensing biological pressure,comprising: an implantable device comprising a first membrane structure,a second membrane structure, and a plurality of nanophotonic componentsadapted to reflect light, wherein the first and second membranestructures are separated by a gap and the first membrane structure ismovable with respect to the second membrane structure in response to achange in ambient pressure such that the implantable device has aresonance wavelength that shifts as a size of the gap changes; and areader unit adapted to transmit optical light to the implantable deviceand detect the resonance wavelength of the implantable device based onlight reflected from the implantable device.
 2. The system of claim 1,wherein the reader unit is adapted to detect the resonance wavelengthbased on a shift in the resonance wavelength of light reflected from theimplantable device.
 3. The system of claim 2, wherein the reader unit isadapted to determine the biological pressure based on the detectedresonance wavelength of the implantable device.
 4. The system of claim1, wherein the implantable device is adapted for implantation into aneye, and wherein the biological pressure is an intraocular pressure. 5.The system of claim 1, wherein the first and second membrane structuresare both deformable in response to the change in ambient pressure. 6.The system of claim 1, wherein the first and second membrane structuresare separated by one or more mechanical flexures.
 7. The system of claim1, wherein the first and second membrane structures are rigid.
 8. Thesystem of claim 1, wherein the nanophotonic components arenanoparticles.
 9. The system of claim 1, wherein the nanophotoniccomponents are embedded in the first and second membrane structures. 10.The system of claim 1, wherein the implantable device is a firstimplantable device, the system further comprising a plurality ofadditional implantable devices, each additional implantable devicehaving the same structure as the first implantable device.
 11. Thesystem of claim 10, wherein each implantable device is coupled toanother implantable device.
 12. An apparatus for sensing biologicalpressure, comprising: an implantable device comprising a first membranestructure, a second membrane structure, and a plurality of nanophotoniccomponents adapted to reflect light, wherein the first and secondmembrane structures are separated by a gap and the first membranestructure is movable with respect to the second membrane structure inresponse to a change in ambient pressure such that the implantabledevice has a resonance wavelength that shifts as a size of the gapchanges, the resonance wavelength being detectable based on lightreflected by the implantable device.
 13. The apparatus of claim 12,wherein the first and second membrane structures are separated by one ormore mechanical flexures.
 14. The apparatus of claim 12, wherein thefirst and second membrane structures are rigid.
 15. The apparatus ofclaim 12, wherein the nanophotonic components are nanoparticles.
 16. Theapparatus of claim 12, wherein the nanophotonic components are embeddedin the first and second membrane structures.
 17. The apparatus of claim12, wherein the implantable device is a first implantable device, theapparatus further comprising a plurality of additional implantabledevices, each additional implantable device having the same structure asthe first implantable device.
 18. The apparatus of claim 17, whereineach implantable device is coupled to another implantable device. 19.The apparatus of claim 12, further comprising a reader unit adapted todetect the resonance wavelength of the implantable device.
 20. Theapparatus of claim 19, wherein the reader unit is adapted to detect theresonance wavelength based on a shift in the resonance wavelength oflight reflected by the implantable device.
 21. The apparatus of claim20, wherein the reader unit is adapted to determine the biologicalpressure based on the detected resonance wavelength of the implantabledevice.
 22. The apparatus of claim 12, further comprising a reader unitadapted to detect the resonance wavelength of the implantable device,the reader unit adapted to transmit a plurality of wavelengths to theimplantable device, and detect the resonance wavelength based on areflected plurality of wavelengths of light reflected by the implantabledevice.
 23. The apparatus of claim 22, wherein the reader unit isadapted to determine the biological pressure based on the detectedresonance wavelength of the implantable device.
 24. The apparatus ofclaim 12, wherein the implantable device is adapted for implantationinto an eye, and wherein the biological pressure is an intraocularpressure.
 25. The apparatus of claim 12, wherein the first and secondmembrane structures are both deformable in response to the change inambient pressure.